NASA's Cassini spacecraft takes its final plunge into Saturn

After traversing the solar system for almost 20 years and delivering a trove of valuable data and gorgeous photos of Saturn, the Cassini spacecraft plunged into the ringed planet's atmosphere Friday on a mission of self-destruction.

At 4:55 am PT, NASA tweeted that it had received the probe's final signal, signifying that it's "now part of the planet it studied." NASA intentionally fired Cassini's thrusters so it would burn up in Saturn's dense atmosphere, rather than crashing it into -- and possibly contaminating -- one of the planet's moons.

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Thomas Zurbuchen, associate administrator for NASA's science mission directorate, called the event the final chapter of an amazing mission. "But it's also a new beginning," he said in a statement. "Cassini's discovery of ocean worlds at Titan and Enceladus changed everything, shaking our views to the core about surprising places to search for potential life beyond Earth."

Launched on Oct. 15, 1997, from Cape Canaveral, Florida, as a joint operation of NASA, the European Space Agency and Italy's space agency, Cassini made 294 orbits of the ringed planet. In January 2005, Cassini successfully landed a probe called Huygens on the surface of Saturn's largest moon, Titan.

Cassini's mission control team at NASA's Jet Propulsion Laboratory in Pasadena, California, marks the end of the spacecraft's historic journey Friday.

NASA/Joel Kowsky

During its journey, Cassini collected half a million images and 600 gigabytes of data. Among its accomplishments are discovering six new moons, flying through a geyser on the moon Enceladus and finding that some of Titan as well as Enceladus hold liquid water and may support life (hence, the no-contamination plan).

Though he called it a bittersweet farewell, Michael Watkins, director of NASA's Jet Propulsion Laboratory in Pasadena, California, praised the mission's incredible wealth of discoveries. The Jet Propulsion Laboratory built Cassini and managed its mission for NASA. And in the end, Cassini got a proper sendoff with a farewell soundtrack provided by astrophysicists.